Partition recovery method

ABSTRACT

There is provided a method and system of maintaining partition information relating a computer disc drive. The method includes detecting partition information which is located in the first sector of a partition of a disc drive and determining if it is valid, and comparing the valid partition information with a corresponding duplicate of the partition information which is located in a reserved area. For valid partition information which is the same as the corresponding duplicate of the partition information, a standard booting procedure for the computer is allowed to continue. For valid partition information which is not the same as the corresponding duplicate partition information, valid partition information is stored in the reserved area. For partition information which is not valid, the invalid partition information is replaced with corresponding duplicate partition information which is valid.

RELATED APPLICATIONS

[0001] This application is related to and claims priority from U.S.Provisional Application Ser. No. 60/218,024, filed on Jul. 12, 2000, andis also a Continuation-in-Part of U.S. patent application Ser. No.09/901,501 filed on Jul. 9, 2001.

FIELD OF THE INVENTION

[0002] This invention relates to partition recovery. It relatesparticularly but not exclusively to a method of maintaining partitioninformation relating to a disc drive and to a system for maintaininginformation relating to partitions in disc drives.

BACKGROUND OF THE INVENTION

[0003] Personal computers (PCs) are used commonly in the fields ofbusiness, finance, academia and industry and in the home. The prevalenceof PCs has become such that users are growing increasingly dependent onthe inbuilt reliability of their computers. This has resulted in usersbecoming complacent when maintaining data and system files and creating“back up” records. Furthermore, users often expect inbuilt retrievalsystems to exist which facilitate reconstruction of the records if asystem failure occurs.

[0004] In general, PCs include at least one disc drive which is used tostore the system's operating system software and data files which arecreated and manipulated in everyday use. In a typical disc drive, datais recorded in a plurality of generally circular concentric tracks onthe surfaces of one or more discs. The discs are axially aligned andmounted to a hub of a spindle motor for rotation. An array of verticallyaligned read/write heads are configured to write to or read from thedisc surfaces. During seek operations, the read/write heads arecontrollably moved from track to track by an actuator assembly, so thatdata can be written to or read from different concentric tracks.

[0005] Along each track, data is stored in addressable sectors. Atypical format usually includes a Master Boot Record (MBR) located atthe very first address, Logical Block Address 0 (LBA0), of the disc. TheMBR is accessed by the host system when it is powered or “booted” up andcontains a partition table which points to primary partitions on thedisc drive.

[0006] A disc drive can be arranged such that it contains up to fourprimary partitions, each of which can be pointed to by the MBR. However,some operating systems restrict partitioning of the disc drive such thatthere is only one primary partition. Extended partitions may be definedif necessary. Furthermore, each primary or extended partition can besubdivided into logical partitions.

[0007] The MBR contained in the primary partition references thelocation of other primary partitions on the disc drive, and the nextadjacent extended partition. An Extended Master Boot Record (EMBR) islocated in the first sector of each extended partition, and provides thelocation of the next extended partition on the disc. Extended partitionscontain a boot sector (beginning in the second sector in the partition)in addition to File Allocation Tables (FATs) which are also referencedby the EMBR.

[0008] In addition to the partition tables, the MBR contains code whichis loaded into the random access memory (RAM) of the computer using theROM-BIOS (read only memory Basic Input/Output System) and which isresponsible for the installation of the operating system when the poweris switched on. The ROM-BIOS generally contains an instruction at itsfirst address location which instructs the system to read the MBR of thefirst primary partition which subsequently results in the retrieval ofcode from the boot sector of that partition. The boot sector instructsthe computer to load the operating system software, which is generallystored in system files and data files in the primary partition, into theRAM. Control is then transferred to the operating system whichcoordinates and controls the functions of the computer's centralprocessing unit (CPU) and peripheral devices.

[0009] FATs keep track of files which are stored in partitions on thedisc drive. The FATs also maintain a set of attributes for each file,such as whether the file is one of a system data set, whether it shouldremain hidden in the directory display, whether it should be archivedthe next time that the disc is backed up and whether the file is readonly, in addition to a date and time stamp which stipulates when thefile was created or last changed. When files are stored, they are placedin sectors on the disc. Many files will not fit into a single sector,and the number of sectors which is required to store a file may not beavailable in adjacent sectors in the partition. Hence the file will needto be stored in sectors which are dispersed throughout the partition indifferent tracks. Furthermore, as additional files are created, deletedand modified, they change in length and may require the use of extrasectors, or may free up one or more sectors.

[0010] The FAT provides a record of the locations of the dispersedsectors which are used to store each file, enabling the operating systemto retrieve file data from these dispersed sectors and reconstruct thefiles accordingly. This method of file storage is spatially efficient asthe sector size can be designated such that it is not so large thatspace is frequently wasted on small files, or so small that many sectorsare required to store each file and time is wasted while the disc headscontinually move to access the next sector in the file. However, filesare often divided up into pieces and scattered all over the disc, and intime the partition becomes fragmented.

[0011] Although disc drive fragmentation and non-contiguous storage offile clusters is usually transparent to the user, they can result inslower file retrieval times. This is because the read operations may beinterrupted by seek operations when the actuator assembly moves theread/write heads to another track to read the sector storing the nextfile cluster. Disc drive fragmentation therefore places an extra load onthe system as the read/write heads must make many accesses to differentlocations or to different tracks in one partition in order toreconstruct a single file. Consequently, system crashes may occur morefrequently.

[0012] Defragmentation and optimization software utilities are availablewith most operating systems, but computer users who are not familiarwith the physical structure and use of their disc drives rarely considerthe importance of frequent defragmentation or disc optimization.

[0013] Occasionally, system errors occur, wherein a FAT is corrupted ordestroyed. Ordinarily, this would mean that data which was stored on thedisc would be irretrievably and permanently lost. However, theimportance of the FAT in data recovery has been recognized, and systemdevelopers have designed disc drives which maintain a copy of each FATin a partition. It has been shown that the probability of both copies ofa FAT being corrupted by the same system error is minimal; hence theduplicate storage method is sufficient for repairing damage done to apartition as a result of a system error. No such precautions have beentaken with the MBR or EMBRs.

[0014] Because each primary partition is pointed to directly by the MBR,the consequence of a corrupt primary partition table in any partitionother than the first primary partition is not deleterious to any primarypartition which lies outside of that partition. The remaining primarypartitions each contain their own MBR which is referenced by thepartition information in the MBR of the first primary partition. As aresult, each primary partition may be referenced independently of otherprimary partitions. If the partition table for the first primarypartition can be recovered, its file system can be restored, and in themeantime, the remaining primary partitions will still be functional.However, many operating systems, when installed on a PC, prevent thestructuring of a disc drive such that there is more than one primarypartition. Since the existence of only one primary partition means thatonly one partition can be referenced by the MBR when the system isbooted up, only one operating system can control the CPU (since a systemcannot be booted from an extended or logical partition). Software isavailable which overrides these limitations, but the regular user of aPC is not likely to use it to create more than one primary partition ontheir disc drive.

[0015] The limitation of having only one primary partition per discdrive does not affect most computer users in an adverse manner, asextended partitions can still be allocated in the disc drive,facilitating organized filing habits and data storage. However, the MBRcannot reference more than one extended partition directly from LBA0.Instead, the MBR is provided with a reference to the boot sector of theprimary partition and the EMBR of the first extended partition. The EMBRof the first extended partition provides a reference to the EMBR of thesecond extended partition, which similarly provides a reference to theEMBR of the third (and final) extended partition.

[0016] The difficulty with the system, as it presently exists, is thatthe corruption or destruction of the MBR in operating systems where onlyone primary partition is permitted results in a loss of all referencesto other partitions in the disc drive. That is, because of theforward-linked nature of the MBR and EMBRs, the MBR is the only recordwhich is able to determine the location of partition tables andsubsequent FATs situated anywhere on the hard drive. Although duplicatesare made of all FATs, they cannot be referenced without the MBR (or EMBRin extended partitions) which directs the operating system to thelocation of these FATs. Current systems provide backup MBRs whicheffectively reinstall the MBR using an auxiliary device such as floppydisc drive or a CD-ROM drive, but this method is ineffective if thestructure of the disc drive has been altered since the back-up MBR wascreated (e.g. if the disc drive has been reformatted and no back-upcreated). Furthermore, reinstallation of the MBR requires significantuser-intervention. Similarly, destruction of an EMBR results in loss ofall references to other extended partitions which are referred to,either directly or indirectly, by that EMBR.

[0017] What the prior art is missing is a method of maintainingpartition information in a disc drive that requires minimal userintervention.

SUMMARY OF THE INVENTION

[0018] A preferred embodiment of the present invention includes a methodof maintaining partition information relating to a disc drive. Themethod includes detecting partition information which is located in thefirst sector of a partition of the disc drive and determining if it isvalid. The valid partition information is compared with a correspondingduplicate of the partition information which is located in a reservedarea. For valid partition information which is the same as thecorresponding duplicate of the partition information, the computercontinues with a standard booting procedure. For valid partitioninformation which is not the same as the corresponding duplicatepartition information, the method involves storing the valid partitioninformation in the reserved area. For partition information which is notvalid, the invalid partition information is replaced with correspondingduplicate partition information which is valid.

[0019] Duplicates of original partition information are created toensure that if original partition information is found to be invalid, abackup version is available with which partition tables and subsequentfile allocation tables and system and data files can be recovered.

[0020] In another embodiment of the present invention, there is provideda system for maintaining information relating to partitions in discdrives. The system includes at least one disc drive and firmware forcontrolling the initialization of the computer and its peripheraldevices. Upon application of power to the disc drive, instructionsembodied in the firmware are executed upon detection of invalidpartition information, redirecting the system to seek valid partitioninformation.

[0021] These and various other features as well as advantages whichcharacterize the present invention will be apparent upon reading of thefollowing detailed description and review of the associated drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0022]FIG. 1 is a top view of an exemplary disc drive in which preferredembodiments of the present invention are implemented.

[0023]FIG. 2 is a flow diagram of a process according to a preferredembodiment of the present invention.

[0024]FIG. 3 is a flow diagram illustrating an alternative embodiment ofthe present invention.

DETAILED DESCRIPTION

[0025] A disc drive 100 constructed in accordance with a preferredembodiment of the present invention is shown in FIG. 1. The disc drive100 includes a base 102 to which various components of the disc drive100 are mounted. A top cover 104, shown partially cut away, cooperateswith the base 102 to form an internal, sealed environment for the discdrive in a conventional manner. The components include a spindle motor106, which rotates one or more discs 108 at a constant high speed.Information is written to and read from tracks on the discs 108 throughthe use of an actuator assembly 110, which rotates during a seekoperation about a bearing shaft assembly 112 positioned adjacent thediscs 108. The actuator assembly 110 includes a plurality of actuatorarms 114 which extend towards the discs 108, with one or more flexures116 extending from each of the actuator arms 114. Mounted at the distalend of each of the flexures 116 is a head 118, which includes an airbearing slider enabling the head 118 to fly in close proximity above thecorresponding surface of the associated disc 108.

[0026] During a seek operation, the track position of the heads 118 iscontrolled through the use of a voice coil motor 124, which typicallyincludes a coil 126 attached to the actuator assembly 110, as well asone or more permanent magnets 128 which establish a magnetic field inwhich the coil 126 is immersed. The controlled application of current tothe coil 126 causes magnetic interaction between the permanent magnets128 and the coil 126 so that the coil 126 moves in accordance with thewell-known Lorentz relationship. As the coil 126 moves, the actuatorassembly 110 pivots about the bearing shaft assembly 112, and the heads118 are caused to move across the surfaces of the discs 108.

[0027] The spindle motor 116 is typically de-energized when the discdrive 100 is not in use for extended periods of time. The heads 118 aremoved over park zones 120 near the inner diameter of the discs 108 whenthe drive motor is de-energized. The heads 118 are secured over the parkzones 120 through the use of an actuator latch arrangement, whichprevents inadvertent rotation of the actuator assembly 110 when theheads are parked.

[0028] A flex assembly 130 provides the requisite electrical connectionpaths for the actuator assembly 110 while allowing pivotal movement ofthe actuator assembly 110 during operation. The flex assembly includes aprinted circuit board 132 to which head wires (not shown) are connected;the head wires being routed along the actuator arms 114 and the flexures116 to the heads 118. The printed circuit board 132 typically includescircuitry for controlling the write currents applied to the heads 118during a write operation and a preamplifier for amplifying read signalsgenerated by the heads 118 during a read operation. The flex assemblyterminates at a flex bracket 134 for communication through the base deck102 to a disc drive printed circuit board (not shown) mounted to thebottom side of the disc drive 100.

[0029] Storage space on a disc 108 may be divided into partitions.Partition information that is located at the lowest logical base address(LBA0) of a first partition of the disc drive 100 is generally referredto as the Master Boot Record (MBR). The MBR contains a program whichsearches the MBR partition table for the location of the partitioncontaining a boot sector which is to be used for initializing theoperating system of the host system. The MBR is located in a primarypartition on the disc drive, which also contains the system files anddata files which are necessary for the installation of the operatingsystem into the Random Access Memory (RAM). The MBR also contains areference to all other primary partitions which are located on the discdrive, and the location of the first adjacent extended partition. Thefirst extended partition whose location follows the primary partition,and each subsequent extended partition thereafter, contains a partitiontable in the first sector known as the extended MBR (EMBR). The EMBRprovides a reference to the boot sector and File Allocation Tables(FATs) within that partition in addition to the starting location of thenext extended partition.

[0030] The Basic Input/Output System (BIOS) controls the initializationof the host system and its peripheral devices, although in some cases itcan be bypassed and other devices can be used to initialize the system.The BIOS may be embodied in the firmware in the form of an erasableprogrammable read only memory (EPROM). The instructions embodied by thefirmware may be in the form of assembly language code which enables thefirmware to interact with the disc drive and other peripheral devicesconnected to the host system.

[0031] In a booting up process, the BIOS instructs the host system toload the operating system from the disc drive into the RAM of the hostsystem. This is achieved by handing control from the BIOS to a bootsector, located using the partition table which is contained in the MBRof the first partition on the disc drive. The system files to which theboot sector refers are then loaded into the RAM. The MBR thus containsthe first piece of code that a host system interprets, after the BIOShas initiated the disc drive upon power-up.

[0032] The present invention complements existing boot procedures byassessing the validity of the partition information, prior to theinstallation of the operating system into the RAM. The BIOS is used toexecute commands which determine the validity of partition informationcontained in the MBR which is the partition record located in the veryfirst sector of the first partition of the disc drive and partitioninformation contained in the first sector of other partitions in thedisc drive.

[0033]FIG. 2 illustrates a process in which partition information ismaintained according to preferred embodiments of the present invention.The system is powered up in step 430 and the validity of the partitioninformation which is located in the first sector of each partition onthe disc drive is determined prior to the operating system softwarebeing installed into the RAM as shown in step 432. This partitioninformation is contained in the MBR of primary partitions and the EMBRof extended partitions. The partition information is validatedpreferably by executing a subroutine which is stored in firmware, suchas the BIOS. Partition information which is not valid includesnonsensical information (for example, refers to sectors or partitionswhich do not exist) and corrupt partition information. Preferably,viruses such as boot-record infectors which are stored with thepartition information and affect the boot process can also be identifiedduring the validation process 432.

[0034] If the partition information contained in the MBR and EMBR isfound to be valid, it is then compared with duplicate partitioninformation which has been stored in a reserved area, as in step 446. Itis preferred that the reserved area is located on the disc drive, and isan area which is not used to store system or data files in the usualeveryday use of the disc drive. Alternatively, the reserved area may beany other area which is capable of storing partition information,including firmware. It is also preferred that the reserved area isequally divided by the number of partitions into which the disc drive isdivided. As an alternative embodiment, there may be partitions on thedisc drive for which there is very little partition information and as aconsequence, the reserved sub-area for that partition may be less thanis required for other partitions.

[0035] If the partition information which is located in the first sectorof each partition matches the duplicate partition information which islocated in the corresponding reserved sub-area, system control is handedback to the BIOS which subsequently hands over to the MBR which locatesthe boot sector for the operating system and the standard boot processcontinues, as illustrated by step 448.

[0036] If the partition information which is located in the first sectorof a partition is valid but does not match the duplicate partitioninformation which is located in the corresponding reserved sub-area,this suggests that the partition information in the MBR or EMBR haschanged since the last time the host system was booted. This change maybe the result of several actions. For example, the host system may havebeen booted from a floppy disc and an alternative operating system mayhave been installed resulting in a consequent change in the contents ofthe MBR. In some cases, the disc drive may have been re-formatted andthe partition information contained in the MBR or an EMBR was altered.There is also the possibility that a system error occurred, and thepartition information was corrupted.

[0037] In such cases, and in the case where any partition information isfound to be invalid, the BIOS may be programmed to instruct the user toinsert a partition recovery program into a peripheral device. Recoveryof the partition information can take place and the system rebooted.

[0038] According to preferred embodiments of the present invention, thefloppy disc inserted by the user is used to instruct the computer toretrieve valid duplicates of the partition information from the reservedarea.

[0039] Upon retrieval of the duplicate partition information, the useris presented with a list of the duplicate partition information and isprompted to select which partition information is to be recovered, as instep 434. The user selects the partition information to be recovered(step 436) and the duplicate partition information then replaces theinvalid partition information which was located in the MBR and/or EMBR(step 38). Recovery can be completed by overwriting the existing MBR andEMBR with the partition information taken from the reserved area 442. Inaddition, using the partition information that is retrieved from thereserved area, the system can be rebooted 444.

[0040] In alternative preferred embodiments, upon the BIOS detectinginvalid partition information in the MBR or EMBR 432, the BIOS itselfexecutes instructions which result in the retrieval of the duplicatepartition information.

[0041] Another preferred embodiment is described with the aid of theflow chart in FIG. 3. On detecting non-matching original and duplicatepartition information 446, a copy of the new partition information isstored in the reserved area (as in step 550). If the reserved area isfull 552, it is preferable that the oldest corresponding partitioninformation is deleted to create sufficient space for the new partitioninformation 554. The new partition information can then be stored in thereserved area 556. If there is space in the reserved area for the newpartition information without deleting the older partition information552, the new partition information can be stored without first deletingan older version of the partition information 556.

[0042] Referring again to FIG. 2, the user is then presented with a listof the duplicate partition information which has been stored in thereserved area (step 434). Again, this can be achieved using acommercially available partition table recovery program. Preferably,this is achieved by executing a code stored in the BIOS which presents alist of the duplicate partition information which has been stored in thereserved area to the user so that the level of user interaction isminimized.

[0043] It is preferred that the duplicate partition information isappended with the date on which it was stored. This enables the user toassess the duplicate partition information and determine which partitioninformation should be recovered and installed back into the MBR or EMBR.The user may select the earliest valid duplicate of the partition tablewhich was stored 436, since a later duplicate will most likely have beenaffected. After the user has selected the desired partition information,the selected partition information replaces the partition information inthe MBR or the EMBR 438 in the recovery process 442. The system is alsorebooted using the selected partition information 440.

[0044] If the disc drive was reformatted such that there were partitionseither created or destroyed, it is possible that the partitioninformation may have been invalid. Thus, in one embodiment of thepresent invention, upon reformatting the disc drive, the duplicatepartition information is updated, ensuring that the latest version ofthe partition information can be recovered, should a system error occurwhich affects the original partition information.

[0045] This system and method provides a back up and recovery of thepartition information that requires relatively less user intervention.

[0046] Alternatively, embodiments of the present invention may bedescribed as follows:

[0047] The present invention provides for a method and system ofmaintaining partition information relating a disc drive 100. When poweris applied to the disc drive 430, partition information which is locatedin the first sector of a partition of a disc drive is detected anddetermined if it is valid 432. The valid partition information iscompared with a corresponding duplicate of the partition informationwhich is located in a reserved area 446. For valid partition informationwhich is the same as the corresponding duplicate of the partitioninformation, the method involves continuing a standard booting procedurefor the computer 448. For valid partition information which is not thesame as the corresponding duplicate partition information, the methodinvolves storing the valid partition information in the reserved area456. For partition information which is not valid, the method involvesreplacing the invalid partition information with partition informationwhich is valid 438.

[0048] The invalid partition information may include partitioninformation which is corrupt, missing, or has been deleteriously alteredby a virus. In one embodiment, the reserved area is a dedicated area onthe disc which is reserved for the purpose of storing duplicatepartition information and which is equally divided by the number ofpartitions which exist on the disc drive. Alternatively, the reservedarea may be located on firmware. The duplicate partition information maybe appended with the date on which it was created. If no space isavailable in the reserved area, the method can include steps of removingthe oldest duplicate partition information from the reserved area 554and storing the newest duplicate partition information therein 556. Inone embodiment, where the partition information is not valid, it isreplaced by corresponding duplicate partition information which is validand which is stored in the reserved area 438. The user may be presentedwith a list of duplicate partition information 434, and the user selectsthe version of corresponding duplicate partition information which willreplace the invalid partition information 436. The instructions whichresult in the presentation of the duplicate partition information to theuser may be contained in a storage medium which is read using aperipheral device, or firmware such as the BIOS.

[0049] It is to be understood that the foregoing disclosure isillustrative only, and changes may be made within the principles of thepresent invention to the full extent indicated by the broad generalmeaning of the terms in which the appended claims are expressed.Although the preferred embodiment described herein is directed to a discdrive for a personal computer, it will be appreciated by those skilledin the art that the teachings of the present invention can be applied toother systems without departing from the scope and spirit of the presentinvention.

1. A method of maintaining partition information relating a disc drive,the method comprising steps of, when the disc drive has power applied toit: (a) detecting partition information which is located in the firstsector of a partition of the disc drive and determining if it is valid;(b) comparing the valid partition information with a correspondingduplicate of the partition information which is located in a reservedarea; (c) for valid partition information which is the same as thecorresponding duplicate of the partition information, continuing astandard booting procedure for the disc drive; (d) for valid partitioninformation which is not the same as the corresponding duplicatepartition information, storing the valid partition information in thereserved area; and (e) for partition information which is not valid,replacing the invalid partition information with partition informationwhich is valid.
 2. The method according to claim 1 in which thedetecting step (a) includes determining partition information which iscorrupt, is missing, or has been deleteriously altered by a virus. 3.The method according to claim 1 further comprising a step (f) ofproviding a dedicated area on a disc of the disc drive reserved for thepurpose of storing duplicate partition information in which thededicated area is equally divided by the number of partitions whichexist on the disc drive.
 4. The method according to claim 1 furthercomprising a step (f) of providing the reserved area on firmware.
 5. Themethod according to claim 1 wherein the duplicate partition informationis appended with the date on which it was created.
 6. The methodaccording to claim 1 in which, if no space is available in the reservedarea, the step (d) further comprises steps of: (f) removing the oldestduplicate partition information from the reserved area; and (g) storingthe newest duplicate partition information therein.
 7. The methodaccording to claim 1 wherein partition information which is not valid isreplaced by corresponding duplicate partition information which is validand which is stored in the reserved area.
 8. The method according toclaim 1 wherein the user is presented with a list of duplicate partitioninformation which has been appended with the date on which it wascreated and which is stored in the reserved area, and the user selectsthe version of corresponding duplicate partition information which willreplace the invalid partition information.
 9. The method according toclaim 8 further comprising a step of executing instructions whichresults in the presentation of the duplicate partition information tothe user, in which the instructions are contained on a disc of the discdrive or on firmware.
 10. A system for maintaining information relatingto partitions in disc drives associated with a computer, the systemcomprising: at least one disc drive; firmware controlling theinitialization of the computer and its peripheral devices; andinstructions installed on the firmware which are executed upon detectionof invalid partition information, the instructions redirecting thesystem to seek valid partition information.
 11. The system according toclaim 10 wherein the disc drive is divided into one or more partitions,each partition containing partition information which relates to the useof sectors within that partition and the location of at least one otherpartition which is located elsewhere on the disc drive.
 12. The systemaccording to claim 10 wherein the firmware controlling theinitialization of the computer is a programmable read only memorydevice.
 13. The system according to claim 10 wherein the firmwarecontrolling the initialization of the computer executes BasicInput/Output System (BIOS) software.
 14. The system according to claim13 wherein the BIOS contains instructions for determining the validityof partition information which is located in the first sector of eachpartition in the disc drive.
 15. The system according to claim 14wherein the BIOS contains further instructions which are executed upondetection of invalid partition information, the instructions comprising:(a) redirecting the system to a reserved area wherein for each partitionin the disc drive, a duplicate of valid partition information has beenstored; (b) presenting the user with duplicates of the valid partitioninformation; (c) enabling the user to select one of the duplicates ofthe valid partition information which will replace invalid partitioninformation; (d) replacing the invalid partition information with thevalid duplicate partition information which has been selected by theuser; and (e) rebooting the computer, using the replaced partitionrecords.
 16. A disc drive comprising: a disc; a set of partitioninformation describing usage allocation on the disc; and means formaintaining the set of partition information.
 17. The disc drive ofclaim 16 in which at least one backup copy of the set of partitioninformation is retained in the disc drive.
 18. The disc drive of claim17 in which the means for maintaining the partition information furtherincludes an executable set of instructions to replace the set ofpartition information with the or one of the backup copies.